Deodorization and odor-removal by using ozone are frequently utilized. Free-hydroxyradical produced by reaction between ozone and water molecule decomposes various odorous substances, especially malodorous substances such as ammonia and isovaleric acid etc. to provide deodorization and odor-removal effects. The free-hydroxyradical is produced by methods (1) ozonolysis caused by ultraviolet radiation, (2) hydrogen peroxide decomposition caused by ultraviolet radiation, (3) ozonolysis caused by hydrogen peroxide catalyst etc., and is produced efficiently by the method (3) in particular.
Incidentally, the above-mentioned method (3) has so far been carried out by putting a matter to be treated into aqueous hydrogen peroxide and making ozone bubble in the aqueous hydrogen peroxide. In this method, however, it has been unable to deodorize and remove odor from a large-scaled matter, and an efficiency has been bad.